When atmospheric air is blown into the reactor of a pyrolysis system, the cooling effect may slow down the pyrolytic reaction taking place and the slag discharging from the base of the reactor may be cooled enough to affect its free flowing discharge. If the air entering the reactor is not preheated more of the carbonaceous material must be burned in this air to produce the necessary high temperatures for pyrolysis to occur effectively. To avoid this, a heat exchanger is used for heating the incoming air utilizing the heat in the process gas discharging from the reactor. This necessitates a large heat exchange unit because of the quantities of air and process gas being utilized and also necessitates controls to maintain the desired air inlet temperature. The heat exchange unit being fabricated from heat resistant material is a high expense part of the device. Further, the process gas must be purged of impurities before entering the exchanger to avoid deposition of foreign matter in the exchanger that would necessitate frequent extensive cleaning or replacement.
Because of the high cost of these pyrolysis systems, it is desirable to avoid any unnecessary accessories. The heat exchanger represents a high cost item that if it can be eliminated would show a significant reduction in the total cost.